Abstract

Objective: Transcranial Magnetic Stimulation (TMS) is a noninvasive technique that stimulates a localized brain region underneath a coil. Recently, the application of repetitive Transcranial Magnetic Stimulation (rTMS) to the primary motor cortex (M1) has been used to promote functional recovery in stroke patients with hemiparesis. High-frequency rTMS (5 Hz or greater) was applied over the affected hemisphere to reactivate hypoactive regions. Because of recent advances in MRI technology and, in particular, the gradient coils, high-frequency whole brain rTMS-fMRI is possible. The use of interleaved rTMS-fMRI during stimulation at a frequency of 5 Hz aids in understanding how the brain is modulated during stimulation. Method: We measured BOLD signal changes in whole brain during interleaved rTMS-fMRI (5Hz) using 3T MRI. Image processing and statistical analyses were carried out using the Statistical Parametric Mapping (SPM8) software. Results: Distinct BOLD signal changes extending to the remote motor network during 5 Hz-rTMS over the M1 were successfully demonstrated using interleaved rTMS-fMRI. Negative BOLD responses were observed in the contralateral M1, the dorsal premotor cortex (PMd), and the bilateral supplementary motor cortex (SMA), even though no significant BOLD signal changes were observed in the stimulated M1. The negative BOLD responses gradually became marked during (3 mins 57 sec). Therefore, long-lasting plastic changes may occur within 4 mins. Negative BOLD responses in remote regions away from the directly stimulated M1 suggest that subthreshold high frequency rTMS over the motor cortex induced neuromodulation via neuronal networks. Conclusion: The remarkable negative BOLD responses in the contralateral M1 induced by high-frequency rTMS may be useful for identifying a treatment strategy involving M1 stimulation.

Highlights

  • Transcranial Magnetic Stimulation (TMS) can stimulate brain underneath a coil noninvasively [1]

  • The remarkable negative Blood Oxygen Level-Dependent (BOLD) responses in the contralateral M1 induced by high-frequency repetitive Transcranial Magnetic Stimulation (rTMS) may be useful for identifying a treatment strategy involving M1 stimulation

  • We describe the effects of subthreshold high-frequency rTMS in directly stimulated M1 and areas distantly connected by neuronal networks. rTMS-Functional Magnetic Resonance Imaging (fMRI) during stimulation at a frequency of 5 Hz is important for understanding treatment strategies using TMS

Read more

Summary

Introduction

Transcranial Magnetic Stimulation (TMS) can stimulate brain underneath a coil noninvasively [1]. The application of rTMS of the primary motor cortex (M1) has been reported to promote functional recovery in stroke patients with hemiparesis due to induced neuroplasticity [2]. RTMS has been considered to modulate the sensorimotor network by either direct M1 stimulation or by an indirect effect through transsynaptic connections. The precise mechanism of its facilitative and inhibitory effects on the sensorimotor network remains uncertain [6]. Functional Magnetic Resonance Imaging (fMRI) studies by M1 TMS demonstrated widespread increases and decreases in Blood Oxygen Level-Dependent (BOLD) signals in cortical and subcortical areas [6-9]. These studies have showed the cortico-cortical and corticosubcortical connections that regulate the sensorimotor network with multisynaptic modulation

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call